Bioremediation is a term used to describe processes which make use of certain types of bacterial microorganisms which "consume" hydrocarbons in the presence of oxygen to convert the hydrocarbon to CO.sub.2 : and water, according to the following general equation: ##STR1## Bioremediation has thus been shown to be an effective method, in general, for treating petroleum contaminated soil (PCS). Bioremediation is being used more commonly in the treatment of PCS due to increasingly stringent state and federal regulations regarding environmental contamination, and particularly regarding underground storage tanks for petroleum and petroleum-based products.
The number of underground petroleum storage tanks in the United States and throughout the world is astounding. Over time, these tanks develop leaks which contaminate the surrounding soil with petroleum hydrocarbons. Since this creates a significant environmental hazard, regulations have been implemented to prevent such contamination and to require the clean up of such contamination.
U.S. Pat. No. 4,850,745 describes an in situ or "on site" bioremediation system in which a leaking tank (containing gasoline or other petroleum hydrocarbon) is removed, leaving a cavity in the ground. The soil remaining in the tank cavity is leveled and dry form bacteria cultures are distributed over the soil surface. Thereafter, a layer of pea gravel is spread over the applied dry culture and a system of distribution piping is laid out on top of the pea gravel. Finally, another layer of pea gravel is placed over the installed piping and fill dirt and reconstruction relating to installation of a new tank takes place. This type of in situ system does not address the reclamation of the contaminated soil which is removed from the site when the tank is removed. Furthermore, systems of this type require construction at every site where a tank is removed. Finally, in high ground water areas this dry remediation approach is inappropriate.
With the continuing emphasis on control and clean up of environmental contamination, bioremediation systems and methods are needed which are centrally located and provide the capacity to reclaim large volumes of PCS with the resulting soil being suitable for reuse subsequent to reclamation thereof, thereby obviating the need to dispose of PCS in landfills or utilize undesirable thermal degradation processes.